1 . Field of the Invention
The present invention relates to a particle measuring apparatus and a particle measuring method by the apparatus, particularly to a particle measuring apparatus and a particle measuring method by the apparatus for measuring blood cells, or particles of latex or cement powder using the electrical-impedance-change detection method for measuring particles in a sample suspension in accordance with a change of electrical impedance by passing the sample suspension through a through-hole.
2. Prior Arts
To measure the particle-diameter distribution of blood cells in blood or industrial particles of cement powder and latex, particle-diameter distribution measurement using the electrical-resistance-change detection method has been performed. In the case of this measurement, a slide plate having a through-hole through which a sample suspension can pass is arranged at a connective portion of a sample vessel to measure and analyze particles passing through the through-hole as disclosed for example, in U.S. Pat. No. 3,783,376. A particle-diameter distribution is obtained by measuring the number of particles by the number of signal pulses generated when particles pass through the through-hole and the volume of a particle by the pulse height. In the case of the above disclosed example, one through-hole is bored on one slide plate.
In the case of the electrical-resistance-change detection method, because a change of the electrical resistance of a sample suspension when a particle passes through the sample suspension is linearly measured, the intensity of signal to be penetrated is proportional to the volume of the particle. However, measurable particle diameter is limited by the through-hole diameter. For example, when the diameter of a particle decreases to 1/30 the through-hole diameter or less, it is difficult to separate a particle signal from noise. On the contrary, when the particle is too large, the through-hole is clogged and thereby the particle is prevented from passing through the through-hole.
Thus, accurate measurement cannot be made. Therefore, to measure samples having a wide particle-distribution, it is necessary to prepare slide plates having through-holes with different diameters and to manually remove and replace slide plates having selected through-holes one by one. Therefore, operation becomes complex and this prevents measurement from being quickly performed.